Moshe Weitzman has been a consistent contributor to Drupal core and Contrib since November 2001 (i.e. before drupal.org was born). As such, he has pretty much touched the whole core code. He maintains the user.module, the bootstrap code, and the groups.drupal.org web site. He is the #1 Drupal developer on Ohloh. He is also a member of the Security team and a Permanent Member of the Drupal Association.
Services: Consulting services include site planning, information architecture (i.e. wireframes), installation, training, and ongoing support. Custom Drupal software development is my specialty. Depending on the size of your project, I may hire subcontractors (with your permission) to implement parts of the site. My minimum fee for a project is US$15,000.
Cyrve. I started a company, Cyrve, which specializes in data migration into Drupal. We do migrations for a living, so why should you struggle through yours? Hire us and enjoy a pain free data migration. Your developers will thank you.
Moshe is intimate with Drupal's inner workings, and can complete custom projects with speed and quality. He is maintainer of the following Drupal areas:
devel module. The sine qua non for drupal developers.
block page visiblity
web server authentication integration
significant system documentation